Hard disk drives are widely used in computer systems to store information. These disk drives have a rigid disk of magnetic material on which binary data may be written and stored for later retrieval. Data is written on the disk by moving a magnetic recording head to a position over the disk where the data is to be stored. The magnetic recording head then generates a magnetic field, which encodes the data into the magnetic material of the disk. Data is read from the disk by similarly positioning the magnetic recording head and then sensing the magnetic field of the disk's magnetic material. The positioning of the magnetic recording head is accomplished by continually spinning the disk while positioning a moveable arm over the surface of the disk. The moveable arm carries the magnetic recording head in a sweeping motion, generally across the radius of the disk. Read and write operations are synchronized with the rotation of the disk to insure that the data is read from and written to the desired location on the disk.
The magnetic recording head is generally encapsulated in a slider, which provides physical support for both the magnetic recording head and the electrical connections between the magnetic recording head and the remainder of the disk drive system. The slider also provides an air-bearing surface which permits the magnetic recording head to "fly" in close proximity to the surface of the spinning disk. As sliders carry the magnetic recording head closer to the disk surface, information may be more closely packed on the disk, increasing the storage capacity of the disk drive system. An important factor in achieving a minimum and predictable flying height of the magnetic recording head over the disk is the surface finish of the slider's air-bearing surface. Sliders having warped or otherwise deformed air-bearing surfaces, or air-bearing surfaces with an improper relation to the surface of the magnetic recording head, impair the performance of disk drive systems.
Sliders, formed from a ceramic wafer, generally have two parallel rails whose bottom surfaces form the air-bearing surface and fly over the spinning disk. The magnetic recording head is mounted within the slider, and extends down through a rail, terminating at the air-bearing surface of the rail. Grinding processes attempt to create a smooth air-bearing surface by removing material from the magnetic recording head and rail surfaces. However, one problem in the production of sliders, referred to as a recession error, or pole tip recession, commonly results from lapping operations where the durability of the magnetic recording head material and that of the slider material differ. When forming the air-bearing surface, the less durable material may be eroded more easily than the other material, resulting in a non-planar air-bearing surface. Various mechanical processes used while producing sliders also induce stresses in the material of individual sliders. These stresses often result in distortions in the slider, such as rails whose air-bearing surfaces are not co-planar due to twisting or cupping of the slider.
In light of the foregoing, it is desirable to have an apparatus for producing very repeatable and very accurate air-bearing surfaces on sliders for disk drives. It is further desirable that this apparatus be inexpensive and simple to use. It is also desirable that this apparatus be capable of finishing the air-bearing surfaces of many sliders simultaneously. It is also desirable that the apparatus be able to correct recession errors in the sliders being finished.